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December 20, 2011

Higg Non-News

Both groups (ATLAS and CMS) found statistically-significant excesses in two channels, corresponding to

H→γγH \to \gamma\gamma

H→ZZ*H\to Z Z^*

with an invariant mass centered around 125 GeV.

The latter decay mode yields a 4-lepton final state where one of the ℓ+ℓ−\ell^+\ell^- pairs has an invariant mass of 91 Gev, corresponding to the decay of an on-shell ZZ (the other ZZ is, necessarily, off-shell). Since the relevant 4-lepton final states have relatively low backgrounds, the experimentalists could have (modestly) improved their results by relaxing their constraint that one of the ZZs be on-shell. My colleague, Can Kiliç, and collaborators have a recent paper advocating exactly such an analysis.

According to Can, this wouldn’t quite have boosted CERN into 5σ5\sigma discovery-territory, but it would have made the result more compelling (or, conversely, less-so, depending on the result).

In fact, Can and co. go a little further, and advocate looking in a number of multi-lepton channels: